This invention is based on the success of identification of the chemical structure of FR-1923 substance. That is, FR-1923 substance is a known antibiotic isolated from the fermentation broth of a strain of the genus Nocardia deposited with the American Type Culture Collection under ATCC No. 21806, the details of which are described for example, in German Patent application No. 2,242,699, which corresponds to U.S. Pat. No. 3,923,977 issued on Dec. 2, 1975.
In said prior literature, the FR-1923 substance is defined by the various physico-chemical properties without any disclosure of its chemical structure. As a result of extensive structural determination study, the inventors of this invention have established the structure of the FR-1923 substance as 1-(.alpha.-Carboxy-4-hydroxybenzyl)-3-(((2-((4-(3-amino-3-carboxypropoxy)p henyl))-2-hydroxyiminoacetamido)))-2-azetidinone of the following formula. ##STR2## The above attractive and unique single .beta.-lactam structure of the antibiotic FR-1923 substance makes the inventors of this invention encouraged to study on chemical syntheses of FR-1923 substance per se and other related new single .beta.-lactam compounds in favour of searching the structure-activity relationship and other active derivatives, analogues or homologues and further any possibility of an industrial synthetic process for the preparation thereof.
From the above viewpoint, the inventors of this invention have synthesized a lot of novel and unique modified compounds of FR-1923 substance and together with have made intensive efforts to prepare some usefull intermediary 3-amino-2-azetidinone compounds, so far as profitable.
For the purpose of illustrating the state of prior arts, the all of limited known related compounds which were synthesized from penicillins by degradative reactions and the relevant literatures are mentioned as follows: ##STR3##